It began starting in 1970 through to the 1980s.

https://fred.stlouisfed.org/blog/2023/03/when-comparing-wages-and-worker-productivity-the-price-measure-matters/

Then in the 1990s is when it flipped.

https://www.economicshelp.org/blog/221939/economics/the-two-speed-us-economy-2026/

You can clearly see in 1970 things were in the much more balanced productive state, and we are in an upside down economy. This will not last much longer with AI.